Treatment of cellulosic matter with activated nitrogen or other activated gases

ABSTRACT

AN IMPROVED PROCEDURE IS PROVIDED FOR THE DELIGNIFICATION AND/OR BLEACHING OF CELLULOSIC MATTER, IN WHICH THE BRIGHTNESS AND/OR STRENGTH PROPERTIES ARE ENCHANCED. THE CELLULOSIC MATTER MAY BE MECHANICAL PULP (STONE OR RE-FINER GROUNDWOOD) WHICH IS AT A HIGH CONSISTENCY OF FROM ABOUT 15 TO ABOUT 95%, OR A CHEMICAL CELLULOSIC PULP WHICH MAY BE UNBLEACHED OR PARTIALLY DELIGNIFIED OR SEMIBLEACHED AND WHICH ALSO IS AT A HIGH CONSISTENCY OF FROM ABOUT PULP, PREFERABLY TO FORM FIBER AGGREGATES HAVTHE PULP, PREFERABLY TO FORM FIBER AND FIBER AGGREGATES HAVING LOW DENSITY, SUBSTANTIALLY UNCOMPACTED POROUS FLUFFED STRUCTURE. THEN FLUFFED PULP IS TREATED WITH A GASEOUS MIXTURECONTAINING AN &#34;ACTIVE&#34; OR ELECRTONICALLY EXCITED&#34; FORM OF ASPECIFIC GAS, NAMELY NITROGEN, HELIUM, NEON ARGON, KRYPTON XENON, SINGLET OXYGEN OR HIGH ENERGY TRIPLE OXYGEN, EITHER ALONE OR IN A MIXTURE WITH, AT THE NORMAL FORM OF THE GAS AND AMMONIA, IF THE GAS IS &#34;ACTIVE NITRIGEN&#34;, UNTIL THE PULP HAS BEEN CONTACTED WITH A SUFFICIENT AMOUNT OF SUCH FORM OF GAS, EG AT LEAST ABOUT 0.1% TO A PRACTICAL UPPER LIMIT OF ABOUT 1 TORR TO A HIGH PRESSURE, LOW PRESSURE, EG OF FROM ABOUT 1 TORR TO A HIGH PRESSURE, E.G., UP TO ABOUT 100 P,S:G., AT A TEMPERATURE RANGING BEBETWEEN ABOUT 20 TO ABOUT 100*C. FOR A PERIOD OF TIME OF APPROXIMATELY 1 TO 0.5 TO ABOUT 13.

FIPSSD? nited States Patent Oflice and to improve the brightness stability of the pulp. The

rs sweetness Int. c1. nzre a/oo US. Cl. 162-65 33 Claims ABSTRACT OF THE DISCLOSURE An improved procedure is provided for the delignification and/or bleaching of cellulosic matter, in which the brightness and/or strength properties are enhanced. The cellulosic matter may be mechanical pulp (stone or refiner groundwood) which is at a high consistency of from about 15 to about 95%, or a chemical cellulosic pulp which may be unbleached or partially delignified or semibleached and which also is at a high consistency of from about 15 to about 95%. The procedure involves flufling the pulp, preferably to form fiber and fiber aggregates having a low density, substantially uncompacted porous fiuffed structure. Then the fluifed pulp is treated with a gaseous mixture containing an active or electronically excited form of aspecific gas, namely nitrogen, helium, neon argon, krypton, xenon, singlet oxygen or high energy triplet oxygen, either alone or in admixture with the normal form of the gas and ammonia, if the gas is active nitrogen, until the pulp has been contacted with a sulficient amount of such form of gas, e.g. at least about 0.1% to a practical upper limit of about 10% by weight, at a low pressure, e.g.. of from about 1 torr to a high pressure, e.g. up to about 10 p.s.i.g., at a temperature ranging between about 20 to about 100 C. for a period of time of approximately 1 to about 60 minutes at a pH from about 0.5 to about 13.

BACKGROUND OF THE INVENTION (1) Field of the invention This invention relates to the delignification and/or bleaching of cellulosic materials. The cellulose materials with which the present invention is concerned are mechanical pulp, chemical pulp and semi-chemical pulp.

Bleaching is a continuation of the cooking process in which the ligneous material and coloring matter remaining in the chemical pulp are removed selectively with as little degradation of the pulp fibers as possible. Bleaching of pulp has advanced to a high degree of sophistication involving single stage and multi-stage procedures. The choice of bleaching agent has traditionally been dependent on whetherthe pulp is a mechanical pulp or a chemical p p- (2) Description of the prior art Mechanical and groundwood pulps have many desirable characteristics for low-cost papers, e.g. high yield, good bulk, high opacity, and good printing properties. The natural brightness of these pulps is, however, too low for the better grades of groundwood content papers. Also, the brightness of unbleached groundwood pulp varies with the species, the wood process, its age and its quality.

,Hence, the need for suitable bleaching processes arose in order to compensate for natural brightness variations of the wood; to obtain still brighter pulp to meet the everincreasing demands for higher quality groundwood papers;

Patented Apr. 23, 1974 e.g. two stages P-Hs or Hs-P or three stage Hs-P-Hs systems.

The bleaching of chemical pulp is accomplished in several stages. A "stage" constitutes a phase starting with addition and reaction of a chemical with a pulp, and ending with the washing of the pulp. Within each stage there are may process variables which are dictated by the type of reaction desired in that particular stage, and the operating conditions of the stage. These variables include: percent of chemical added and consumed, chemical concentration, consistency, temperature, time and pH. A series of such stages is called a bleaching sequence.

In such multi-stage bleaching process, the first operation for the removal of, lignin and other encrustants-usually following the digestion stage and the subsequent washing stage in a kraft, soda or sulfite processconsists in treating the pulp aqueous suspension with elemental chloride; in aqueous solution. Chlorination of the unbleached pulp so changes the ligneous impurities that they become in part soluble in water while, of the portions not readily soluble in water, a part is soluble in alkaline solutions such as dilute sodium hydroxide.

Among the agents used to bleach chemical pulp are ele-= mental chlorine, chlorine dioxide, hypochlorites, chlorites, peroxides, chlorates, bichromates, and permanganates, as well as reducing agents, e.g. sulfurous acid, bisulfites, di= thionites, and borohydrides. However, for chemical pulps (e.g. those made by the vkraft, sulfite or soda processes) the bleaching agents traditionally used are chlorine and chlorine dioxide, usually used in a multi-stage process. The first step thus usually consists of treating the pulp in an aqueous suspension with chlorine in solution in the aqueous phase. Chlorine dioxide may be used either in admixture with the chlorine, or in replacement of the chlorine, in this first stage. The next stages usually consist of a Washing stage, preferably an alkaline washing or ex= traction stage. The products of pulp chlorination and of the oxidative bleaching stages are more soluble in an alkaline medium than in water, and they are generally taken out of the system by an alkaline extraction. For the attainment of brightness with strength preservation, for brightness stability and bleaching economy, the reaction products resulting from chlorination and oxidative bleaching are removed as they are formed in those opera-= tions by means of alkaline extraction. Caustic soda is the preferred agent, but other alkalis have been used.

Regardless of the number of stages, the treatments on the pulp are generally .carried out in slurry form at low consistencies ranging from about 3 to about 15% and at times varying from about 30 minutes to about 5 hours and at temperatures ranging from ambient to about C. Due to the low consistency of the wood pulp being treated with the reagents in these multi-stage bleaching processes, rates of reaction are slow and retention in each stage is therefore long. This results in large equipment, large quantities of material in process, difliculty of con= trol because of the large time lag, and waste chemicals consumed in secondary actions which contribute nothing to the overall multi-stage bleaching process.

The assignee of the present applicants, Pulp and Paper Research Institute of Canada, owns several patents which provide an elfective solution of this problem of the bleach= ing of chemical pulps by the use of a high consistency gaseous phase bleaching. The patents show the treatment of chemical pulp with chlorine, chlorine dioxide, chlorine monoxide, ozone-peroxides, and ammonia, at a high consistency in the range of about 15 to about 60% by comminuting the high consistency pulp and treating such comminuted pulp with gaseous reagents instead of with the aqueous solutions which had been used before. By such technique, reaction times were very much reduced, chemical usage was reduced and the bleached pulp yield was increased. These patents include the following:

Number Country Issue date Inventors 733,012 Canada..... April 26, 1966 F. H. Yorston and N.

Liebergott.

3,586,599.... U.S.A June 22, 1971 Do.

752,864 Canada...-. February 14, 1967. N. Liebergott and F.

H. Yorston.

3,742,731.... U.S.A October 14, 1969.. 0.

787,810 Canada...-- June 18, 1968 F. H. Yorston, N.

Liebergott and R. M. A. T. de Montigny.

849,982 ..do August 25, 1970 D. W. Clayton, R.

M. A. 'I. de Montigny and N. Liebergott.

3,617,432.-.. U.S.A.....-. September 2, 1971... Do.

869,267 Canada..... April 27, 1971 N. Liebergott, F. H. Yorston, R. M. A. T. de Montigny and J. E. Tasman.

3,630,828.... U.S.A December 28, 1971... Do.

899,005 Canada. May 2,1972 N. Ltebergott and H.

. er. 3,619,349.... U.S.A September 9, 1971... Do.

(3) Aims of the invention None of the above-described procedures provided a truly universally effective bleaching agent. An object, then, of a main aspect of this invention is to provide a pulp bleaching procedure which is equally effective and useful for both mechanical and chemical pulps.

The invention also aims, in another of its aspects, to provide a simple, effective process for the bleaching of chemical pulp in which a caustic washing step may be eliminated.

The invention aims, in another of its aspects, for the provision of such a process for both mechanical and chemical pulps where brightness and/or strength proper ties are enhanced.

SUMMARY OF THE INVENTION (1) Broad statements of the invention Applicant has found that a bleaching agent for such improved process is provided by an active or electronically excited form of a gas selected from the group consisting of nitrogen, helium, neon, argon, krypton, xenon, singlet oxygen and high eergy oxygen triplet. Thus, by a broad aspect of this invention, there is provided, in a process for the delignification and/or'bleaching of cellulosic matter, the improvement which comprises subjecting such cellulosic matter while it is in the form of a low density substantially uncompacted flulfed structure and at a consistency of about 15% or more to a delignification and/or bleaching amount, e.g., at least about 0.1% by weight of the cellulosic matter on an oven dry basis (o.d.) of an active or electronically excited form of a gas selected from the group consisting of nitrogen, helium, neon, argon, krypton, xenon, singlet oxygen and high energy oxygen triplet. The term an active or electronically excited form of a gas selected from the group consisting of nitrogen, helium, neon, argon, krypton, xenon, singlet oxygen and high energy oxygen triplet as used herein refers to any atomic form, and/or any ionic form, and/or any excited form of, the respective gas, namely nitrogen, helium, neon,-argon, krypton, xenon or oxygen, or a combination of these, which is of sufiicient lifetime that it may be removed from the region in which it is formed, or if it is in a static system, remains long enough after the excitation is stopped, to permit reaction with cellulosic matter. Active or electronically ex cited nitrogen, helium, neon, argon, krypton or xenon is produced by passing the respective gas through an arc, glow or corona discharge which can occur in various types of equipment. The quantity of the active gas produced depends upon the type of equipment, pressure, electric field and current density. Active or electronically excited nitrogen, helium, neon, argon, krypton or xenon as well as active or electronically excited singlet oxygen or high energy oxygen triplet is also produced by passing the respective gas or, for nitrogen, ammonia gas through an electrodeless discharge, or through a microwave dis-= charge, or through a condensed pulsed discharge or by a plasma jet.

(2) Variants of the invention By another broad aspect of this invention, a process is provided for the bleaching of mechanical pulp (stone or refiner groundwood) which comprises: providing a pulp having a consistency of from about 15 to about 95%; flufiing the pulp; and thereafter treating the fluffed pulp with a gaseous mixture containing an active or electronically excited form of a gas selected from the group consisting of nitrogen, helium, neon, argon, krypton, xenon, singlet oxygen and high energy oxygen triplet, namely a bleaching amount, e.g. at least about 0.1% by weight to a practical maximum of about 10% by weight, at a low pressure of, e.g. from about 1 torr to a high pressure up to, e.g. about 10 p.s.i.g., at a temperature of from about 20 to about 100 C. for a period of from about 1 to about 60 minutes, and at a pH from about 0.5 to about 13.

By another aspect of the present invention, a process is provided for the bleaching of a fibrous chemical cellulosic pulp, which comprises: providing an unbleached or partially delignified or semi bleached pulp at a high consistency of about 15 to about 95%; fiufiing said pulp; and then contacting the fluffed pulp with sufficient active or electronically excited" form of a gas selected from the group consisting of nitrogen, helium, neon, argon, krypton, xenon, singlet oxygen and high energy oxygen triplet, namely a bleaching amount, in a mixture containing an active or electronically excited form of a gas selected from the group consisting of nitrogen, helium, neon, argon, krypton, xenon, singlet oxygen and high energy oxygen triplet, with normal gas respectively, or ammonia with active nitrogen, e.g. at least about 0.1% to a practical maximum of about 10% by weight, at a low pressure of, e.g. from about 1 torr to a high pressure up to, e.g. about 10 p.s.i.g., at a temperature of from about 20 to about C. for a period of from about 1 to about 60 minutes and at a pH of from about 0.5 to about 13.

Other gases may be provided in active or electronically excited stages. For example, hydrogen may be so provided by passing it through a corona discharge. However, such active hydrogen would be exceedingly and explosively dangerous to use. Similarly, fluorine, chlorine, bromine and iodine may be made active. How ever, their use is not desirable because they add undesirable halide ions to the wood pulp.

The amount of the active or electronically excited form of a gas selected from the group consisting of nitrogen, helium, neon, argon, krypton, xenon, singlet oxygen and high energy oxygen triplet used is at least about 0.1% by weight. The maximum amount is not critical since any amount will be operative and hence the cost will determine the amount used. A practical amount would hence be of the order of about 7 to about 10% by weight.

DESCRIPTION OF EXAMPLES OF THE INVENTION The following are comparative examples showing unexpected advances over the prior art obtained by the practice of aspects of this invention.

(1) Specific description Example 1.-Chemical pulp: Unbleached kraft pulp from coniferous wood, characterized by Kappa number 24 and a 0.5% C-ED viscosity of 19 was pressed to 30% consistency. The pulp was comminuted into fiber and I fiber aggregates using the apparatus described in US. Pat. No. 3,630,828, issued Dec. 28, 1971.

Samples of the prepared pulp were treated in the following manner:

Example 1(a).-One portion of the pulp was treated with chlorine gas for 1 minute (2.8% chlorine on oven dried pulp). The pH of the chlorinated pulp was 1.2. The pulp was then diluted to 1% consistency with deionized water. The washing eflluent was removed from the pulp and the color, BOD and COD measured by apropriate tests. The results obtained are shown in Table I.

Example 1(b).-The chlorinated pulp was then extracted with dilute sodium hydroxide (2% NaOH on oven dried pulp at consistency for 1 hour at 60 C.). The pulp was then diluted to 1% consistency with deionized water. The washing efiluent was removed from the pulp and the color, BOD and COD measured by appropriate tests. The pulp was then made into handsheets and the brightness, Kappa number and CED viscosity measured. The results obtained are shown in Table I.

Example 1(c).0ne portion of the unbleached pulp was placed into a rotary vessel. Nitrogen was passed into the rotary vessel for 45 minutes at a rate of 3 liters/min. The pH of the moist pulp was 5.0. The pulp was then washed and made into handsheets and the brightness, Kappa number and CED viscosity measured. The results obtained are shown in Table I.

Example l(d).-One portion of the unbleached pulp was placed into a rotary vessel. Nitrogen gas 3 liters/ min. at 8 p.s.'i.g. was passed through a corona discharge where it was acted upon by a primary potential of 120 volts. The gaseous mixture of active nitrogen so formed and the carrier nitrogen was passed into the rotary vessel under atmospheric pressure for 45 minutes. The pH of the moist fiuffed pulp at the end of the reaction was 2.7, and the temperature of the pulp was 25 C. The pulp was then diluted to 1% consistency with de-ionized water. The washing efiluent was removed from the pulp and the color, BOD and COD measured by the appropriate tests.

One-half of the active nitrogen treated and washed pulp was made into handsheets and the brightness, Kappa number and CED viscosity measured. The results obtained are shown in Table I.

Example 1(e).The other half of the treated pulp from Example 1(d) above was extracted with dilute sodium hydroxide (2% NaOH o.d. pulp at 10% consistency for 1 hour at 60 C.) and then washed with deionized water at 1% consistency. The washing efiluent was removed from the pulp and the color, BOD and COD measured by appropriate tests. The pulp was then made into handsheets and the brightness, Kappa number and CED viscosity measured. The results obtained are shown in Table I.

Example 1(f).One portion of the unbleached pulp was placed into a rotary vessel which was placed into a water bath, and the pulp heated to 80 C. Nitrogen gas, 3 liters/min., at 8 p.s.i.g., was passed through a corona discharge, where it was acted upon by a primary poten= tial of 120 volts. The gaseous mixture of active nitrogen and the carrier nitrogen was passed into the rotary vessel under atmospheric pressure for 45 minutes. The pH of the moist, flutfed pulp, at the end of the reaction, was 2.0, and the temperature of the pulp was 80 C. The pulp was then diluted to 1% consistency with de-ionized water. The washing effiueht was removed from the pulp, and the color, BOD and COD measured by the appropriate tests. One-half of the active nitrogen-treated and washed pulp was made into handsheets, and the bright- 6 ness, Kappa number and CED viscosity measured. The results obtained are shown in Table 1.

Example 1(g).-The other half of the active nitrogen,

pulp, from Example 1(f) above, was extracted with dilute sodium hydroxide (2% NaOH on o.d. pulp) at 10% consistency, for 1 hour at 60 C., and then washed with deionized water at 1% consistency. The washing efiluent was removed from the pulp, and the color, BOD and COD measured by appropriate tests. The pulp was then made into handsheets, and the brightness, Kappa number and CED viscosity measured. The results obtained are shown in Table 1.

Example 1(h).A sample of the unbleached pulp mentioned previously in Example 1(f) was pressed to 35% consistency, and then shredded in the apparatus disclosed in the above-identified US. patent. A portion of this pulp was treated with an aqueous solution of sodium carbonate (2% sodium carbonate on pulp), and then reshredded and fiuffed as in Example 1, at 30% consistency. The pump was then placed into a rotary vessel. Nitrogen gas, at a rate of 3 liters/min., at 8 p.s.i.g., was passed through a corona discharge, where it was acted upon by a primary potential of volts. The gaseous mixture of active nitrogen so formed and the carrier nitrogen was passed into the rotary vessel at atmospheric pressure for 45 minutes. The pH of the moist flutfed pulp, at the end of the reaction, was 10.2, and the temperature of the pulp was 26 C. The pulp was then diluted to 1% consistency with de-ionized water. The washing efiiuent was removed from the pulp, and the color, BOD and COD measured by the appropriate tests. The results obtained are shown in Table I.

One-half of the active nitr0gen-treated and washed pulp so produced was made into handsheets, and the brightness Kappa number and CED viscosity measured. The results are shown in Table I.

Example 1(i) .The other half of the active nitrogentreated pulp from Example 1(h) was extracted with dilute sodium hydroxide, 2% NaOH on o.d. pulp, at 10% consistency, for 1 hour at 60 C., and then the pulp was washed. The pulp was then made into handsheets, and the brightness, Kappa number and CED viscosity meas ured. The results obtained are shown in Table I.

Example 1(j).-One portion of the unbleached and fiuffed pulp was placed into a rotary vessel. Nitrogen gas, at a rate of 3 liters/min, at 700 torr pressure, was passed through a corona discharge where it was acted upon by a primary potential of 120 volts. A gaseous mixture of active nitrogen so formed and the carrier nitrogen was passed into the rotary vessel at a pressure of 700 torr for 45 minutes. The pH of the moist, flutfed pulp, at the end of the eaction, was 2.2, and the temperature of the pulp was 22 C. The pulp was then diluted to 1% consistency with de-ionized water. The washing effluent was removed from the pulp and the color, BOD and COD measured by appropriate tests. The results obtained are shown in Table I.

One-half of the active nitrogen-treated and washed pulp was made into handsheets, and the brightness, Kappa number and CED viscosity measured. The results ob-= tained are shown in Table I.

Example 1(k).The other half of the active nitro gen-treated pulp [from Example 1(j)] was extracted with diluted sodium hydroxide (2% NaOH on o.d. pulp) at 10% consistency for 1 hour, at a temperature of 60 C., and then washed with de-ionized water at 1% consistency. The washing efiiuent was removed from the pulp, and the color, BOD and COD measured by appropriate tests. The pulp was then made into handsheets and the brightness, Kappa number and CED viscosity measured. The results obtained are shown in Table I.

Example 1(1).The nitrogen which was used for the above tests to produce the active nitrogen" was only 99.7% pure, so that the remaining 0.3 could be oxygen.

This means that as the gas was passed through a corona discharge, some ozone may have been produced from the small oxygen feed. To check this premise, and to verify that the reduction in Kappa number of the active nitrogen-treated pulp was solely due to this species, unbleached kraft pulp, at 30% consistency, was placed into a rotary vessel. Oxygen, at a rate of 0.009 1iter/min., at 8 p.s.i.g., was passed through a corona discharge, where it was acted upon by a primary potential of 120 volts. The gaseous mixture of ozone so formed and the carrier oxygen was passed into the rotary vessel under atmospheric pressure for 45 minutes. The pH of the moist, tiuiied pulp, at the end of the reaction time, was 7.2; the temperature was 75 C. The pulp was then washed with de-ionized water. The ozone-treated pulp was made into handsheets, and the brightness, Kappa number and CED viscosity measured. The results obtained are shown in Table I.

tower containing the pulp for 4 minutes. The pH of the pulp at the end of the reaction was 3.6 and the temperature of the pulp was 26 C. The pulp was then washed with water and made into handsheets and the Kappa number measured. The Kappa number of the "active argon-treated pulp was 10.8.

The results in Example 1(m) indicate the utility of the invention at very low pressures. The results in Example TABLE I.--PROPERTIEB F KRAFT PULP Conditions Properties of pulp Color of efllucnt 1 Treat- OED Eirepho mcnt 'Iemperavisbright- APHA U.V. Example time ture, End Kappa cosity ness units, COD, BOD, lignin number Pulp treatment (min) O. pH number" cps. cps. mg.Pt/i. ppm. p.p.m. g./1.

Control... Ori ginal pulp 24 19.6 27.3 Ha; Ch orination and wash 1. 2 ......H. 670 386 1(b Pulp from is) plus caustic ex- 6.1 19.2 28.2 1840 806 traction an wash. 1 cl....... Nitrogen alone. 46 24 6.0 23.9 19.5 27.9 1 d) Actve n i trogcn plus nitrogen 46 26 2.7 8.4 18.3 60.1 125 100 an was 1(a) Pulp from 1(d) plus caustic ex- 6.9 18.6 48.3 174 186 traction and wash. 1(i) "At tive nifirogen" plus nitrogen 46 80 2.0 6.0 18.1 66.3 162 121 p us was 1(g) Pulp from 1(1) plus caustic er- 4.4 18.6 62.8 163 172 traction plus wash. 1(h) "Active nitrc en" plus wash 46 10. 2 18.0 19.2 82. 2 40. 2 1(i).. Pulp irom 1 plus caustic ex- 16.0 19.2 30.1

traction plus wash. 1(1) Active nitro en" plus nitrogen 46 22 2.2 8.0 18.9 60.8 129 111 72 26 at 700 torr p us wash. 0. 1(k) Pulp from 1(i) plus caustic ex- 6.6 18.9 48.9 176 182 71 43 traction and wash. 1(l) Comparative example using 02/0: 45 25 1.2 22.0 19.0 28.6

mixture.

1 Pulp diluted to 1% consistency.

Kappa number, as measured by C.P.P.A. Standard G.18.

' CED viscosity, as measured by C.P.P.A. Standard G.24P.

Elrepho brightness, as measured by C.P.P.A. Standard E1.

5 Color, APHA units, mg. Pt/L, absorption measured at 450 mu. COD, p.p.m., as measured by C.P.P.A. Standard H3P.

' BOD, p.p.rn., as measured by C.P.P.A. Standard 11.2.

B Lignin, g./l., absorption measured at 205 mu.

Caustic extraction-standard conditions, 2% NaOH on pulp (oven dried basis), 10% pulp consistency, 60 minutes at 60 C.

Example 1(m).Unbleached kraft pulp from coniferous wood, characterized by Kappa number 32.0 and 0.5% CED viscosity 26 cps. was pressed to 30% consistency. The pulp was comminuted into fiber aggregates using the apparatus described in US. Pat. No. 3,630,828, issued Dec. 28, 1971. One portion of the unbleached fiuifed pulp was placed into a stationary reaction tower. The tower was connected to an apparatus similar to the apparatus described by Gartaganis and Winkler, Canadian Journal of Chemistry, p. 1458, vol. 34, 1956. The apparatus and the reaction tower was evacuated to 1 torr. Nitrogen gas, 3 liters/min, was passed through the corona discharge where it was acted upon by a primary potential of 85 volts. The gaseous mixture of active nitrogen so formed and the carrier gas passed through the reaction tower containing the pulp for minutes. The pH of the pulp at the end of the reaction period was 2.6 and the temperature of the pulp was 26 C. The pulp was then washed with water, made into handsheets and the Kappa number measured. The Kappa number after the active nitrogen treatment was 4.7.

Example l(n).-A portion of the unbleached kraft pulp mentioned in Example 1(m) was placed in a sta= tionary reaction tower and evacuated to 1 torr. Argon gas, 3 liters/min, was passed through the corona discharge where it was acted upon by a primary potential of 55 volts. The gaseous mixture of active argon so formed and a carrier gas was passed through the reaction duced in the corona reaction.

Example 2.-Mechanical pulp: A commercial sprucebalsam mechanical pulp, having an initial brightness of 56.2, was pressed to 35% consistency and communited into fiber and fiber aggregates, using an apparatus as shown in assignees U.S. Pat. No. 3,630,828, issued Dec. 28, 1971.

Example 2(a).A portion of the comminuted pulp was placed into a rotary vessel which was set in a bath and the temperature of the bath was maintained at 25 C. Nitrogen gas was passed into a rotary vessel at atmospheric pressure for 45 minutes at a rate of 3 liters/min. The final pH of the pulp was 5.8. A portion of the treated pulp was washed and air dried and the brightness measured. The brightness tab were then placed in a hot air circulatory oven at C. for one hour, then conditioned in a constant atmosphere, having a relative humidity of 50% at 70 C. The brightness after the aging treatment was measured. The brightness, the brightness after aging, and the strength properties of the pulp tested on standard handsheets are set out in Table II below.

Example 2(b).--A portion of the untreated comminuted pulp was placed into a rotary vessel which was set in a bath and the temperature maintained at 25 C. Nitrogen gas, 3 liters/min. at 8 p.s.i.g., was passed through a corona dicharge where it was acted upon by a primary potential of 60 volts. In these experiments, the discharge apparatus used was Welsbach laboratory Model T-408.

The gaseous mixture of active nitrogen" so formed and the carrier nitrogen was passed into the rotary vessel at atmospheric pressure for 30 minute. The pH of the moist comminuted pulp after treatment was 4.6. A portion of the treated pulp was washed and air dried and the brightness measured. The brightness tabs were then placed in a hot air circulatory oven at 105" C. for one hour, then conditioned in a constant atmosphere at arelative humidity of 50% at 70 F. The brightness after the aging treatment was measured. The brightness, the brightness after aging, and the strength properties of the pulp tested on standard handsheets are set out in Table II below.

Example 2(c) .-A portion of the untreated comminuted pulp was placed in a rotary vessel which was set in a bath and the temperature maintained at 50 C. Nitrogen gas, 1 liter/min. at 8 p.s.i.g. was passed through a corona discharge where it was acted upon by a primary potential of 120 volts. The gaseous mixture of active nitrogen'so formed and the carrier nitrogen was passed into the rotary vessel at atmospheric presure for 30 minutes. pH of the moist comminuted pulp after treatment was 4.2. A portion of the treated pulp was washed and air dried and the brightness measured. The brightness tabs were then placed in a hot air circulatory oven at 105; C. for one hour, then conditioned in a constant atmosphere at a relative humidity of 50% at 70 F. The brightness after the aging treatment was measured. The brightness, the brightness after aging, and the strength properties of the pulp tested on standard handsheets are set out in Table II below. I

10 um, neon, argon, krypton, xenon, singlet oxygen and high energy oxygen triplet.

2. A process for the bleaching of chemical pulp which comprises: providing the pulp at a consistency of from about 15 to about 95%; fiufling the pulp; and thereafter contacting the fluffed pulp with a gaseous mixture con= taining at least 0.1% by weight of the pulp on an oven dry basis, an active or electronically excited form of a gas selected from the group consisting of nitrogen. helium, neon, argon, krypton, xenon, singlet oxygen and high energy oxygen triplet, at a pressure which is selected from a low pressure up to a high pressure, at a tempera ture of not greater than about 100 C. for a period of time of about 1 minute to not greater than about 60 minutes at a pH not exceeding about 13.

3. The process of claim 2 wherein the active or elec= tronically excited form of agas selected from the group consisting of nitrogen, helium, neon, argon, krypton, xenon, singlet oxygen and high energy oxygen triplet is active nitrogen.

4. The process of claim 2 wherein the active" or electronically excited form of a gas selected from the group consisting of nitrogen, helium, neon, argon, kryp= ton, xenon, singlet oxygen and high energy oxygen triplet is active argon.

5. The process of claim 3 wherein the chemical pulp is lunbleached or partially delignified or semi-bleached pu p.

6. The process of claim 4 wherein the chemical pulp is 1unbleached or partially delignified or semi-bleached pu p.

7. The process of claim 3 wherein the active nitrogen is absorbed on, or reacts with, the flufi'ed pulp until about 0.1 to about 10% by weight of the pulp on an oven dry basis has been absorbed or reacted on the pulp.

8. The process of claim 3 wherein the reaction is car= ried out at a pressure of about 1 torr to about 10 p.s.i.g.

9. The process of claim 4 wherein the reaction is carried out at a pressure of about 1 torr to about 10 p.s.i.g.

TABLE IL-PROPER'IIES 0F MECHANICAL PULP Conditions or treatment Properties of plup Elrepho Treatbrightness ment Tempera- Breaking Elrepho after Example time ture, End Bulk, length, Tear brightness, aging number Pulp treatment (min.) 0. pH cc./g. 1 M I ctor a percent percent Control No treatment 3. 34 2, 799 61 65. 6 64. 5 25 5. 8 3. 23 2, 782 63 56. 0 65. 0 30 25 4. 6 3. 10 8, 462 72 68. 5 57. 5 30 4. 2 2. 18 5, 047 64 60. 8 59. 7

1 Bulk, ce./g., as measured by P.P.R.I.C. Standard PB-4.

The preceding examples can be repeated with similar success by substituting the generically andspecifically described reactants and operating conditions of this invention for those used in the preceding examples.

From the foregoing description, one skilled in the art can easily ascertain the essential characteristics of this invention, and without departing from the spirit and scope thereof, can make various changes and modifications of the invention to adapt it to various usages and conditions. Consequently, such changes and modifications are properly, equitably, and intended to be, within the full range of equivalence of the following claims.

We claim:

1. In a process selected from the delignification and the bleaching of cellulosic matter, the improvement which comprises subjecting such cellulosic matter, while it is in the form of a low density substantially uncompacted flutfed structure and at a consistency of about 15% or more to a delignification or bleaching with at least about 0.1% by weight of the cellulosic matter on an oven dry basis, of an -active" or electronically excited form of a gas selected from the group consisting of nitrogen, heli- 10. The process of claim 3 wherein the reaction is car= ried out at a temperature of about 20 C. to about C.

11. The process of claim 4 wherein the reaction is carried out at a temperature of about 20 C. to about 100 C.

12. The process of claim 3 wherein the terminal pH of the treated cellulosic material is about 0.5 toabout 13.

13. The process of claim I}, wherein the active nitrogen is in admixture principally ,yvith nitrogen gas.

14. The process of claim 7 wherein the reaction conditions are as follows: the pressure of the reaction is from about 1 torr to about 10 p.s.i.g.; the temperature is about 20 C. to about 100 C.; the absorption or reaction time between the active nitrogen and the cellulosic material is about 1 to about 60 minutes; the pH is about 0.5 to about 13; and the active nitrogen is in admixture principally with nitrogen gas.

15.,.The processof claim '7 wherein the absorption or reaction on the flutfedpulp with a'gaseous mixture of ac-= tive nitrogen" and nitrogen takes place under atmospheric pressure for about 45 minutes, at a temperature of about 25 C. and a terminal pH of about 2.7.

16. The process of claim 7 wherein the absorption or reaction on the fluffed pulp with a gaseous mixture of active nitrogen and nitrogen takes place under atmospheric pressure for about 45 minutes, at a temperature of about 80 C. and a terminal pH of about 2.0.

17. The process of claim 7 wherein the absorption or reaction on the fluffed pulp with a gaseous mixture of active nitrogen and nitrogen takes place under atmospheric pressure for about 45 minutes, at a temperature of about 26 C. and a terminal pH of about 10.2.

18. The process of claim 7 wherein the absorption or reaction on the fluffed pulp with a gaseous mixture of active nitrogen and nitrogen takes place at a pressure of about 700 torr, for a time of about 45 minutes, at a temperature of about 22 C. and a terminal pH of about 2.2.

19. The process of claim 4 wherein the active argon is absorbed on, or reacts with, the fiuifed pulp until about 0.1 to about by weight of the pulp on an oven dry basis has been absorbed on, or reacted on, the pulp and wherein said reaction takes place at a pressure of about 1 torr, for a time of about 4 minutes at a temperature of about 26 C. and at a terminal pH of about 3.6.

20. In a process for bleaching cellulosic pulp involving the steps of bleaching with a bleaching agent, followed by a caustic extraction step and a water washing step, the improvement of using, as the bleaching agent, an active" or "electronically excited form of a gas selected from the group consisting of nitrogen, helium, neon, argon, krypton, xenon, singlet oxygen and high energy oxygen triplet whereby the caustic extraction step may be obviated.

21. The process of claim 20 wherein the active" or electronically excited" form of a gas selected from the group consisting of nitrogen, helium, neon, argon, krypton, singlet oxygen and high energy oxygen triplet is active nitrogen."

22. The process of claim 20 wherein the active or electronically excited form of a gas selected from the group consisting of nitrogen, helium, neon, argon, krypton, xenon, singlet oxygen and high energy oxygen triplet is active argon.

23. A process for the bleaching of stone or refiner groundwood mechanical pulp which comprises: providing the pulp at a consistency of from about to about 95%; flufiing the pulp; and thereafter treating the flutfed pulp with a gaseous mixture containing at least 0.1% by weight of the pulp on an oven dry basis of an active or electronically excited form of a gas selected from the group consisting of nitrogen, helium, neon, argon, krypton, xenon, singlet oxygen and high energy oxygen triplet, at a low pressure up to a high pressure, at a temperature of not greater than 100 C. for a period of time of about 1 minute to not greater than 60 minutes and at a terminal pH not greater than 13.

24. The process of claim 23 wherein the active or electronically excited form of a gas selected from the group consisting of nitrogen, helium, neon, argon, krypton, xenon, singlet oxygen and high energy oxygen triplet is active nitrogen."

25. The process of claim 23 wherein an active or electronically excited form of a gas selected from the group consisting of nitrogen, helium, neon, argon, krypton, xenon, singlet oxygen and high energy oxygen triplet is acti-ve argon."

26. The process of claim 24 wherein the active nitrogen is absorbed on, or reacts with, the fiutr'ed pulp until 0.1 to 10% by weight on an oven dry basis has been absorbed or reacted on the pulp.

27. The process of claim 23 wherein the reaction is carried out at a pressure of about 1 torr to about 10 p.s.i.g.

28. The process of claim 23 wherein the reaction is carried out at a temperature of about 20 C. to about 100 C.

29. The process of claim 23 wherein the terminal pH is about 0.5 to about 13.

30. The process of claim 24 wherein the active nitrogen is admixture principally with nitrogen gas.

31. The process of claim 24 wherein the reaction conditions are as follows: the pressure of the reaction is from about 1 torr to about 10 p.s.i.g.; the temperature is about 20 C. to about 100 C.; the absorption or reaction time between the active nitrogen and the cellulosic material is about 1 to about minutes; the terminal pH of the treated cellulosic material is about 0.5 to about 13; and the active nitrogen is in admixture principally with nitrogen gas.

32. The process of claim 24 wherein the absorption or reaction on the fiuffed pulp with a gaseous mixture of "active nitrogen and nitrogen takes place at atmospheric pressure for a time of about 30 minutes and a terminal pH of about 4.6.

33. The process of claim 24 wherein the absorption or reaction on the fiutfed pulp with a gaseous mixture of active nitrogen and nitrogen takes place at atmospheric pressure for a time of about 30 minutes and a terminal pH of about 4.2.

References Cited UNITED STATES PATENTS 1,903,962 4/1933 Dreyfus 162-63 3,472,731 10/ 1969 Liebergott et a1. 162-63 3,586,599 6/1971 Yorston et al. 162-63 X 3,726,756 4/1973 Polak 162-50 3,740,311 6/ 1973 Liebergott et a1 16265 1,972,608 9/1934 Uhlmann et a1. 8107 ROBERT L. LINDSAY, 111., Primary Examiner A. DANDREA, JR., Assistant Examiner US. Cl. X.R. s 107, 111; 162-50, 63 

